lst-0037-book.cpp
// https://godbolt.org/z/E6MWxY1f7
#include <array>
int main() {
std::array<int, 5> arr5{}; // literal and thus a constant expression
std::array<int, 2+3> arr23{}; // 2+3 can be evaluated by the compiler
const size_t SIZE = 5; // defines a constant
std::array<int, SIZE> arrSC{}; // can often be used by the compiler
size_t size = 7;
std::array<int,size> arrVar{}; // you cannot use a variable
}